Packaged IC device comprising an embedded flex circuit on leadframe, and methods of making same

ABSTRACT

A device is disclosed which includes a flexible material including at least one conductive wiring trace, a first die including at least an integrated circuit, the first die being positioned above a portion of the flexible material, and an encapsulant material that covers the first die and at least a portion of the flexible material. A method is disclosed which includes positioning a first die above a portion of a flexible material, the first die including an integrated circuit and the flexible material including at least one conductive wiring trace, and forming an encapsulant material that covers the first die and at least a portion of the flexible material, wherein at least a portion of the flexible material extends beyond the encapsulant material.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.11/676,578, filed Feb. 20, 2007, now U.S. Pat. No. 7,816,778, which isincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Technical Field

This subject matter disclosed herein is generally directed to the fieldof packaging of integrated circuit devices, and, more particularly, to apacked IC device comprising an embedded flex circuit and various methodsof making same.

2. Description of the Related Art

Integrated circuit technology uses electrical devices, e.g.,transistors, resistors, capacitors, etc., to formulate vast arrays offunctional circuits. The complexity of these circuits requires the useof an ever-increasing number of linked electrical devices so that thecircuit may perform its intended function. As the number of transistorsincreases, the integrated circuitry dimensions shrink. One challenge inthe semiconductor industry is to develop improved methods forelectrically connecting and packaging circuit devices which arefabricated on the same and/or on different wafers or chips. In general,it is desirable in the semiconductor industry to construct transistorswhich occupy less surface area on the silicon chip/die.

In the manufacture of semiconductor device assemblies, a singlesemiconductor die is most commonly incorporated into each sealedpackage. Many different package styles are used, including dual inlinepackages (DIP), zig-zag inline packages (ZIP), small outline J-bends(SOJ), thin small outline packages (TSOP), plastic leaded chip carriers(PLCC), small outline integrated circuits (SOIC), plastic quad flatpacks (PQFP) and interdigitated leadframe (IDF). Some semiconductordevice assemblies are connected to a substrate, such as a circuit board,prior to encapsulation. Manufacturers are under constant pressure toreduce the size of the packaged integrated circuit device and toincrease the packaging density in packaging integrated circuit devices.

The assembly of a semiconductor device and a leadframe and dieordinarily includes bonding of the die to a paddle of the leadframe, andwire bonding the bond pads on the die to the inner leads, i.e., leadfingers, of the leadframe. The inner leads, semiconductor die and bondwires are then encapsulated, and extraneous parts of the leadframeexcised. In one illustrative example, the leadframe strip comprises athin metal foil that is configured for the mounting of one or moresemiconductor die, e.g., one on each die mount paddle. The leadframestrip also includes parallel spaced side rails formed with a pattern ofregistry holes to facilitate handling by automatic machinery. Inaddition, the leadframe strip includes an arrangement of inner leadsconfigured for attachment to the bond pads of the semiconductor dieduring a wire bonding step. The outer leads of the leadframe stripfunction as the external leads of the completed semiconductor devicepackage for connection to an external device or structure, e.g., acircuit board. The leads are connected to the side rails by dam bars,and supported thereby. The die mount paddles are typically connected toeach of the side rails by a paddle support bar, extending transverselywith respect to the centerline of the leadframe strip.

Such traditional packaging techniques and arrangements may not be ableto meet the demands for more densely packaged integrated circuit devicesdesired by semiconductor manufacturers and their customers.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be understood by reference to the followingdescription taken in conjunction with the accompanying drawings, inwhich like reference numerals identify like elements, and in which:

FIGS. 1-13 are various views of an illustrative packaged integratedcircuit device that includes a leadframe and flex circuit that may beemployed as described herein;

FIGS. 14 and 15 are cross-sectional views depicting other possiblestacking arrangements of packaged integrated circuit devices using thetechniques disclosed herein; and

FIGS. 16 and 17 depict another packaged integrated circuit device thatincludes an illustrative leadframe and flex circuit that may be employedas described herein.

While the subject matter disclosed herein is susceptible to variousmodifications and alternative forms, specific embodiments thereof havebeen shown by way of example in the drawings and are herein described indetail. It should be understood, however, that the description herein ofspecific embodiments is not intended to limit the invention to theparticular forms disclosed, but on the contrary, the intention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

Illustrative embodiments of the invention are described below. In theinterest of clarity, not all features of an actual implementation aredescribed in this specification. It will of course be appreciated thatin the development of any such actual embodiment, numerousimplementation-specific decisions must be made to achieve thedevelopers' specific goals, such as compliance with system-related andbusiness-related constraints, which will vary from one implementation toanother. Moreover, it will be appreciated that such a development effortmight be complex and time-consuming, but would nevertheless be a routineundertaking for those of ordinary skill in the art having the benefit ofthis disclosure.

Although various regions and structures shown in the drawings aredepicted as having very precise, sharp configurations and profiles,those skilled in the art recognize that, in reality, these regions andstructures are not as precise as indicated in the drawings.Additionally, the relative sizes of the various features and dopedregions depicted in the drawings may be exaggerated or reduced ascompared to the size of those features or regions on fabricated devices.Nevertheless, the attached drawings are included to describe and explainillustrative examples of the subject matter disclosed herein.

FIGS. 1-3 are top views depicting an illustrative leadframe 100 and flexcircuit 200 that may be employed for the purposes described herein. Theschematically depicted leadframe 100 shown in FIGS. 1-3 is intended tobe representative of any of a variety of different types of leadframestructures that are employed in packaging integrated circuit devices. Ingeneral, the leadframe 100 comprises a plurality of lead fingers 102with illustrative bond pads 104 formed thereon. The exact number andarrangement of the lead fingers 102 may vary depending upon theparticular application. The leadframe 100 also comprises a plurality ofstructures 106, e.g., tie bars, dam bars, that, as described more fullybelow, may be employed in coupling the flex circuit 200 to the leadframe100. In the depicted embodiment, the structures 106 have a surface 106Sthat may be positioned in approximately the same plane as that of thelead fingers 102. Notably, in the disclosed example, the leadframe 100does not employ a paddle or die support structure in the interior region108 of the leadframe 100. However, the present disclosure should not beconsidered as limited to the illustrative arrangement depicted in FIG. 1in which the interior region 108 is substantially free of any structure.

The schematically depicted flex circuit 200 is also intended to berepresentative of any of a variety of different flex circuit devices ormaterials that are commonly employed in the packaging or manufacture ofintegrated circuit devices or products incorporating such devices. Theillustrative flex circuit 200 comprises a body 201 having a firstsurface 201F and a second surface 201S that are on opposite sides of theflex circuit 200. The flex circuit 200 further comprises a plurality ofillustrative bond pads 204 and a plurality of electrical connectorarrays 205A, 205B that are formed on opposite ends of the flex circuit200. Each of the illustrative arrays 205A comprise a plurality ofelectrical connectors 206. In one illustrative example, the arrays 205define a ball grid array assembly that is well known to those skilled inthe art. Electrical connection between the bond pads 204 and an array205 may be provided by a plurality of conductive traces 208 formed in oron the body 201 of the flex circuit 200. The arrays 205 are providedsuch that one or more integrated circuit devices (not shown in FIG. 2)may be conductively coupled to the flex circuit 200, as described morefully below. Of course, the exact number, position, arrangement andlayout of the arrays 205 on the flex circuit 200 may vary depending uponthe particular application. In a general sense, the illustrative flexcircuit 200 is a relatively flexible material that comprises at leastone conductive wiring trace.

As shown in FIG. 2, the flex circuit 200 is positioned above andmechanically coupled to the leadframe 100. In the illustrative exampledepicted herein, the flex circuit 200 may be mechanically coupled to theleadframe 100 by an adhesive material (not shown) that may be applied tothe surfaces 106S of the structures 106. Of course, it should beunderstood that the structures 106 are intended to be representative innature in that the flex circuit 200 may be mechanically coupled to anyportion of the leadframe 100 using any of a variety of known techniques.It should also be understood that, when it is stated herein that adevice or structure may be mechanically coupled or electrically coupledto another device or structure, the coupling may be accomplished bydirect contact between the coupled components or one or moreintermediate structures, circuits or devices may be employed tomechanically or electrically couple the components to one another.

As shown in FIG. 3, an integrated circuit device 300 is positioned aboveand operatively coupled to the flex circuit 200. In one illustrativeexample, the integrated circuit device 300 is mechanically coupled tothe flex circuit 200 using an adhesive material 305 (see FIG. 4). Ofcourse, the integrated circuit device 300 may be mechanically coupled tothe flex circuit 200 using any of a variety of known techniques, e.g.,tape, epoxy, etc. The illustrative integrated circuit device 300comprises a plurality of illustrative bond pads 304 that may be employedto electrically or conductively couple the integrated circuit device 300to other integrated circuits or devices. Traditional bonding wires 350,352 may be employed to electrically or conductively couple theillustrative bond pads 304, 204 and 104 using any of a variety of knowntechniques. The integrated circuit device 300 depicted herein isintended to be representative in nature. That is, the techniques andstructures disclosed herein may be employed in situations where theintegrated circuit device 300 comprises any of a variety of differenttypes of integrated circuit devices, e.g., a memory device, a logicdevice, a microprocessor, an application specific integrated circuit,etc.

Next, as shown in FIGS. 5-7, an encapsulant material 360 is formed inaccordance with known techniques. The encapsulant material 360 coversthe die 300 and portions of the flex circuit 200. The encapsulantmaterial 360 may be a mold compound, an epoxy, etc. The encapsulantmaterial 360 has a first outer or top surface 361T and a second outer orbottom surface 361B. A first outer surface 331 of the die 300 is alsodepicted in FIGS. 12-13. One of the purposes of the encapsulant material360 is to protect the integrated circuit device 300 and the associatedelectrical components connected to the device 300 from environmental orstructural damage. As can be seen in FIGS. 5 and 7, portions of the flexcircuit 200 extend beyond the encapsulant material 360. For referencepurposes, these portions are labeled as 220A and 220B. In theillustrative embodiment depicted herein, the portions 220A, 220B of thecircuit 200 extending beyond the encapsulant material 360 areapproximately symmetrical. However, as will be recognized by thoseskilled in the art after a complete reading of the present application,the portions 220A, 220B may be symmetrical or there may be only a singleportion of the flex circuit 200 that extends beyond the encapsulantmaterial.

As shown in FIGS. 8-9, one or more additional integrated circuit devices400A, 400B may be operatively coupled to the flex circuit 200 via thearrays 205A, 205B, respectively. In the depicted example, the integratedcircuit devices 400A, 400B comprise a first or top surface 404 and aplurality of conductive balls 402 (see FIG. 9) that are adapted toconductively engage the structures 206 on the flex circuit 200.Techniques for establishing such a conductive connection between theintegrated circuit devices 400A, 400B and the flex circuit 200 are wellknown to those skilled in the art. Thus, the illustrative techniquesdepicted herein for conductively coupling such components togethershould not be considered a limitation of the present invention. As withthe integrated circuit device 300, the illustrative integrated circuitdevices 400A, 400B may be any type of integrated circuit device and theycan perform any electrical function. In one particular example, theintegrated circuit device 400A and/or 400B may be an applicationspecific integrated circuit or a controller. It should also beunderstood that terms such as upper, lower and the like are employed ina relative, not absolute sense.

Next, as shown in FIGS. 10-13, the flex circuit 200 is folded such thatthe first or top surface 404 of the integrated circuit devices 400A,400B (see FIG. 9) may be positioned proximate or above the other firstouter surface 361T of the encapsulant material 360. In this illustrativeexample, the integrated circuit devices 400A, 400B are positioned in aside-by-side arrangement above the surface 361T of the encapsulantmaterial 360. In an illustrative example, an adhesive material or tape405 may be employed to secure the integrated circuit devices 400A, 400Bto the encapsulant material 360. Again, although two illustrativedevices 400A, 400B are depicted in the disclosed embodiment, the subjectmatter disclosed herein may be employed where only a single integratedcircuit device is coupled to a portion of the flex circuit 200 thatextends beyond the encapsulant material 360. Moreover, it is notrequired that the entirety of the integrated circuit devices 400A, 400Bbe positioned above the surface 361T of the encapsulant material 360.Rather, in some applications, it may be sufficient that something lessthan the entirety of the integrated circuit devices 400A, 400B may bepositioned above the encapsulant material 360.

FIGS. 14-15 depict alternative arrangements whereby the structures andtechniques disclosed herein may be employed in stacking integratedcircuit devices in a variety of different arrangements. For example, asshown in FIG. 14, another illustrative integrated circuit device 500comprised of a plurality of illustrative conductive connectors 504,e.g., a ball grid array, and a first or top surface 501T may bepositioned above and coupled, both electrically and mechanically, to thesecond surface 201S of the body 201 of the flex circuit 200. Theintegrated circuit device 500 may be a single device or it may be one ormore devices that are separate from one another, like the integratedcircuit devices 400A, 400B depicted in FIG. 14. FIG. 15 depicts anillustrative arrangement whereby the surface 201F of the flex circuit200 may be mechanically coupled to the surface 361T of the encapsulantmaterial 360, and thereafter one or more integrated circuit devices 500may be mechanically and electrically coupled to the flex circuit 200. Asbefore, the illustrative integrated circuit device 500 is intended to berepresentative of any type of integrated circuit device.

FIGS. 16 and 17 depict another illustrative leadframe 100A that may beemployed with a flex circuit 200 as described herein to create apackaged integrated circuit device. As shown in FIG. 16, the leadframe100A has a plurality of extended lead fingers 102A. In the leadframe100A depicted in FIG. 16, the bond pads 104 are asymmetrically spacedaround the leadframe 100A as compared to the leadframe 100 depicted inFIG. 1. In FIG. 17, the illustrative integrated circuit device 300A hasa plurality of bond pads 304A that are also asymmetrically positionedaround the integrated circuit device 300A. A plurality of wire bonds 355are employed to establish the desired electrical connection among thevarious components. Thus, the techniques disclosed herein may beemployed in packaging integrated circuit devices 300A having anasymmetrical pattern of bond pads 304A.

1. A microelectronic device, comprising: a leadframe having a pluralityof lead fingers; a flexible circuit having a first portion correspondingto the leadframe and a second portion extending beyond the leadframe,the first portion having a plurality of bond sites at a first surfaceand a second surface attached to the leadframe; an encapsulant on thefirst surface and covering at least a part of the first portion of theflexible circuit, wherein at least a part of the second portion of theflexible circuit is above the encapsulant; and a plurality of wirebondsextending between corresponding lead fingers of the leadframe and thebond sites of the flexible circuit.
 2. The microelectronic device ofclaim 1 wherein: the leadframe includes two longitudinal membersextending between two transverse members, at least one of the transversemembers carrying the plurality of lead fingers; the second portion ofthe flexible circuit extends beyond the longitudinal members of theleadframe in a first direction; the flexible circuit includes a thirdportion extending beyond the longitudinal members of the leadframe in asecond direction opposite the first direction; the second and thirdportions of the flexible circuit individually include a plurality ofelectrical connectors; the flexible circuit further includes a pluralityof traces electrically coupling at least some of the bond sites at thefirst portion and the electrical connectors at the second and/or thirdportions; the microelectronic device further includes: a first dieattached to the first portion with an adhesive; a second die attached tothe second portion with a first conductive ball; a third die attached tothe third portion with a second conductive ball; and an encapsulantencapsulating the first die and a part of the first portion of theflexible circuit; and the second die and the third die are attached toan outer surface of the encapsulant in a side-by-side arrangement. 3.The microelectronic device of claim 1 wherein: the leadframe includestwo longitudinal members extending between two transverse members, atleast one of the transverse members carrying the plurality of leadfingers; and the second portion of the flexible circuit extends beyondthe longitudinal members of the leadframe.
 4. The microelectronic deviceof claim 1 wherein: the leadframe includes two longitudinal membersextending between two transverse members, at least one of the transversemembers carrying the plurality of lead fingers; the second portion ofthe flexible circuit extends beyond the longitudinal members of theleadframe in a first direction; and the flexible circuit furtherincludes a third portion extending beyond the longitudinal members ofthe leadframe in a second direction opposite the first direction.
 5. Themicroelectronic device of claim 1 wherein: the leadframe includes twolongitudinal members extending between two transverse members, at leastone of the transverse members carrying the plurality of lead fingers;the second portion of the flexible circuit extends beyond thelongitudinal members of the leadframe in a first direction; the flexiblecircuit further includes a third portion extending beyond thelongitudinal members of the leadframe in a second direction opposite thefirst direction; and the second and third portions of the flexiblecircuit individually include a plurality of electrical connectors. 6.The microelectronic device of claim 1 wherein: the leadframe includestwo longitudinal members extending between two transverse members, atleast one of the transverse members carrying the plurality of leadfingers; the second portion of the flexible circuit extends beyond thelongitudinal members of the leadframe in a first direction; the flexiblecircuit includes a third portion extending beyond the longitudinalmembers of the leadframe in a second direction opposite the firstdirection; the second and third portions of the flexible circuitindividually include a plurality of electrical connectors; and theflexible circuit further includes a plurality of traces electricallycoupling at least some of the bond sites at the first portion and theelectrical connectors at the second and/or third portions.
 7. Themicroelectronic device of claim 1 wherein: the leadframe includes twolongitudinal members extending between two transverse members, at leastone of the transverse members carrying the plurality of lead fingers;the second portion of the flexible circuit extends beyond thelongitudinal members of the leadframe in a first direction; the flexiblecircuit includes a third portion extending beyond the longitudinalmembers of the leadframe in a second direction opposite the firstdirection; the second and third portions of the flexible circuitindividually include a plurality of electrical connectors; the flexiblecircuit further includes a plurality of traces electrically coupling atleast some of the bond sites at the first portion and the electricalconnectors at the second and/or third portions; and the microelectronicdevice further includes a first die attached to the first portion, asecond die attached to the second portion, and a third die attached tothe third portion.
 8. The microelectronic device of claim 1 wherein: theleadframe includes two longitudinal members extending between twotransverse members, at least one of the transverse members carrying theplurality of lead fingers; the second portion of the flexible circuitextends beyond the longitudinal members of the leadframe in a firstdirection; the flexible circuit includes a third portion extendingbeyond the longitudinal members of the leadframe in a second directionopposite the first direction; the second and third portions of theflexible circuit individually include a plurality of electricalconnectors; the flexible circuit further includes a plurality of traceselectrically coupling at least some of the bond sites at the firstportion and the electrical connectors at the second and/or thirdportions; and the microelectronic device further includes a first dieattached to the first portion with an adhesive, a second die attached tothe second portion with a first conductive ball, and a third dieattached to the third portion with a second conductive ball.
 9. Themicroelectronic device of claim 1 wherein: the leadframe includes twolongitudinal members extending between two transverse members, at leastone of the transverse members carrying the plurality of lead fingers;the second portion of the flexible circuit extends beyond thelongitudinal members of the leadframe in a first direction; the flexiblecircuit includes a third portion extending beyond the longitudinalmembers of the leadframe in a second direction opposite the firstdirection; the second and third portions of the flexible circuitindividually include a plurality of electrical connectors; the flexiblecircuit further includes a plurality of traces electrically coupling atleast some of the bond sites at the first portion and the electricalconnectors at the second and/or third portions; the microelectronicdevice further includes: a first die attached to the first portion withan adhesive; a second die attached to the second portion with a firstconductive ball; a third die attached to the third portion with a secondconductive ball; and an encapsulant encapsulating the first die and apart of the first portion of the flexible circuit; and the second dieand the third die are attached to an outer surface of the encapsulant.10. A microelectronic device, comprising: a leadframe having a pluralityof lead fingers; a flexible circuit having a plurality of bond sites ata first surface and a second surface attached to the leadframe, a firstportion of the flexible circuit generally corresponding to the leadframeand a second portion of the flexible circuit extending beyond theleadframe; a first die attached to the first portion of the flexiblecircuit; a plurality of wirebonds extending between corresponding leadfingers of the leadframe and the bond sites of the flexible circuit; anencapsulant on the first surface of the flexible circuit covering thefirst die and a part of the first portion of the flexible circuit, atleast a part of the second portion of the flexible circuit being abovethe encapsulant; and a second die attached to the second portion of theflexible circuit and to the encapsulant.
 11. The microelectronic deviceof claim 10 wherein the second portion of the flexible circuit is bentsuch that the second die is above the encapsulant.
 12. Themicroelectronic device of claim 10 wherein the second portion of theflexible circuit is bent such that the second portion is facing thefirst portion and the second die is above the encapsulant.
 13. Themicroelectronic device of claim 10 wherein: the encapsulant at leastpartially encapsulates the first die, the encapsulant having an outersurface facing away from the first portion of the flexible circuit; andthe second portion of the flexible circuit is bent such that the secondportion is facing the outer surface of the encapsulant and the seconddie is adhered to the outer surface of the encapsulant.
 14. Themicroelectronic device of claim 10 wherein the encapsulant at leastpartially encapsulates the first die, the encapsulant having an outersurface facing away from the first portion of the flexible circuit; thesecond portion of the flexible circuit is bent such that the secondportion is facing the outer surface of the encapsulant; and themicroelectronic device further includes an adhesive tape between thesecond die and the outer surface of the encapsulant.
 15. A method forassembling a microelectronic device, comprising: attaching a flexiblecircuit to a leadframe having a lead finger, the flexible circuit havinga first portion corresponding to the leadframe and a second portionextending beyond the leadframe, the flexible circuit including a bondsite at a first surface and a second surface attached to the leadframe;attaching a microelectronic die to the first portion of the flexiblecircuit; forming a wirebond between the lead finger of the leadframe andthe bond site of the flexible circuit; and covering the microelectronicdie and at least a part of the first portion of the flexible circuitwith an encapsulant, at least a part of the second portion of theflexible circuit is above the encapsulant.
 16. The method of claim 15wherein: the microelectronic die is a first microelectronic die; and themethod further includes attaching a second microelectronic die to thesecond portion of the flexible circuit and to the encapsulant.
 17. Themethod of claim 16 wherein attaching the second die includes: attachingthe second die to the second portion of the flexible circuit; bendingthe second portion of the flexible circuit with the attached second diesuch that the second die is above an outer surface of the encapsulant;and attaching the second die to the outer surface of the encapsulantwith an adhesive.
 18. The method of claim 16 wherein attaching a seconddie includes: attaching a first side of the second die to the secondportion of the flexible circuit with a conductive ball; bending thesecond portion of the flexible circuit with the attached second die suchthat a second side of the second die is above an outer surface of theencapsulant, the second side being opposite the first side; andattaching the second side of the second die to the outer surface of theencapsulant with an adhesive.
 19. The method of claim 16 wherein theflexible circuit further includes a third portion extending beyond theleadframe, and wherein the method further includes attaching a thirdmicroelectronic die to the third portion of the flexible circuit and tothe encapsulant.
 20. The method of claim 16 wherein the flexible circuitfurther includes a third portion extending beyond the leadframe, andwherein the method further includes: attaching a third microelectronicdie to the third portion of the flexible circuit; bending the second andthird portions of the flexible circuit with the attached second andthird microelectronic dies such that the second and thirdmicroelectronic dies are above an outer surface of the encapsulant andgenerally side-by-side; and attaching the second and thirdmicroelectronic dies to the outer surface of the encapsulant with anadhesive.